Fuse Pins-Designed so that if an engine seizes with all the turning mass inside the engine that it seperates at the pylon and departs than to take the entire wing off!
You got the right idea but the wrong specification. Engine seizure is not a design parameter for sizing these pins. The pins, in the pylon, are sized against aircraft loads (gusts, flutter, etc.).
The engine mounts against the engine, are sized for the anticipated results of a (single failure condition) fan blade off, and the aircraft designer simply ensures that the blade-off load will not exceed the specified design margin already incorporated in the pin.
A little confusing, but the pin may still fail if other conditions are present.